TripAdvisor, Wayfair and pet-food maker Nutrish on Thursday became the first major brands to say they will stop advertising on Laura Ingraham's Fox News program in response to the host's mockery of a school shooting survivor from Parkland, Fla.

The targeted student, David Hogg, is trying to pressure other companies to abandon Ingraham, too, but history shows that advertiser boycotts of highly-rated Fox News shows are difficult to pull off.

The clearest example of a successful boycott is last year's exodus by commercial sponsors of Bill O'Reilly's program. Though O'Reilly hosted the top-rated show on cable news, dozens of advertisers ditched him after the New York Times reported that five women who accused him of sexual harassment or inappropriate conduct had received a combined $13 million in settlements over the years.

In the final days of “The O'Reilly Factor,” shrinking ad blocks featured promos for a vest with 26 pockets and a freeze dryer for an alien apocalypse.

It is worth remembering, however, that before his firing, O'Reilly survived multiple efforts to organize advertiser boycotts of his show during two decades at Fox News. And it is possible that he would have survived another if the network had not been in damage-control mode nine months after ousting longtime chairman Roger Ailes amid sexual-harassment accusations.

A second example of a successful boycott is the gradual corporate shunning of Glenn Beck over the course of 21 months. The African American advocacy group Color of Change called for advertisers to pull commercials from Beck's Fox News show in July 2009, after Beck said President Barack Obama was “a racist” who “has a deep-seated hatred for white people.”

Beck remained on the air until April 2011, as his advertiser base eroded. Other factors contributed to his program's cancellation, too, including sharp criticism from fellow conservatives such as Pat Buchanan and William Kristol and complaints by Jewish leaders who objected to his habit of comparing political opponents to Nazis.

Boycott efforts against other Fox News personalities have failed to gain momentum. In one memorable episode, Keurig last fall joined a small number of companies in announcing plans to withdraw commercials from Sean Hannity's show.

Hannity responded by egging on fans who filmed themselves destroying Keurig coffee makers, and Keurig ultimately said that “the decision to communicate our short-term media actions on Twitter was done outside of company protocols. Clearly, this is an unacceptable situation that requires an overhaul of our issues response and external communications policies and the introduction of safeguards to ensure this never happens again. Our company and brand reputations are too valuable to be put at risk in this manner.”

Around the same time, Volvo tweeted that it would stop advertising on Hannity's show — then deleted the tweet.

A website called FoxNewsBoycott.com, used to organize a “boycott of the month,” urging visitors to contact companies that advertise on the network. More recently, the Twitter hashtags #BoycottTucker and #BoycottFoxandFriends have not produced results.

At any given time, someone is probably trying to boycott a Fox News show for something. Hogg, who has quickly become a prominent gun-control advocate, is in a better position than most to exert real pressure on advertisers, but his task is a hard one.